Seismic performance of post-and-beam timber buildings II: reliability evaluations

This paper presents an approach to evaluate the performance reliability of post-and-beam timber buildings under seismic excitation. The uncertainties considered include those associated with the earthquake ground motions, the structural mass and shear wall characteristics. The approach uses a verified structural model called “PB3D” for the creation of a database of seismic responses, which are then represented by appropriate response surfaces. These, in turn, are used to formulate explicit performance functions for the reliability analysis. Performance is studied in terms of peak inter-story drift, and polynomial functions are used to represent the seismic response surfaces. Non-performance probabilities are evaluated with respect to different performance expectations, using FORM and importance sampling methods. Case studies for two multi-story post-and-beam buildings are also presented.     

正交胶合木结构抗震研究进展

正交胶合木(CLT)结构板材物理特性良好,与连接件有效配合,在地震条件下抗震性能表现优越。通过分析欧洲和加拿大最新修订的CLT结构标准,对减震系数q和超强度系数γRd进行论述。同时,针对部分CLT结构试验测试结果,按连接件、剪力墙和整体结构分类展开讨论,并阐述了抗震技术领域最新研究成果,以期为正交胶合木结构抗震性能研究提供参考。     

正交胶合木横纹承压性能研究现状

正交胶合木（CLT）在木结构建筑中应用越来越广泛,特别是在中高层建筑物中。CLT作为楼盖构件使用时,承受柱或墙体施加的垂直荷载,因此CLT产品的设计及应用需要其横纹承压弹性模量和强度方面的参数;改善CLT横纹承压性能,也可以提高整体结构强度和建筑安全系数。文中主要介绍目前CLT横纹承压性能测试方法,总结CLT横纹承压性能影响因素方面的研究进展,以期为国内CLT研究提供参考。     

Seismic performance of post and beam timber buildings I: model development and verification

This paper presents a structural model called “PB3D” to perform nonlinear time history analyses of post and beam timber buildings under seismic loads. The model treats the three-dimensional structure as an assembly of roof/floor diaphragms and wall subsystems. The roof/floor diaphragms are modeled by beam elements and diagonal brace elements in order to take into account the in-plane stiffness. The wall system consists of vertical beam elements, for wall posts, as well as nonlinear shear springs to consider the contribution of diagonal wall bracing members or sheathing panels. The hysteretic characteristics of the shear springs are represented by a simplified, mechanics-based model named a “pseudo-nail”. Standard finite element procedure is used to construct the system’s equation of motion, which is solved by Newmark’s integration. The model was verified against shake test results of a three-story post and beam building subjected to strong ground motions scaled to the 1995 Kobe earthquake. Model predictions agreed very well with the test results in terms of base shear forces and inter-story drift responses. This model provides a robust and efficient tool to study the seismic behavior of post and beam timber buildings.     

正交胶合木结构建筑发展现状及影响因素

近年来,正交胶合木（CLT）建筑在欧美地区得到广泛应用并向全球推广。文中从厂商分布、CLT应用、产业协同等方面对当前CLT的发展现状进行梳理,从环保意识、森林资源、政策法规和成本造价等方面对影响CLT建筑发展的主要因素进行对比,分析CLT建筑在我国发展所面临的障碍与机遇,并结合欧美地区的经验对我国CLT建筑的发展进行展望。研究发现,意识认知缺乏、市场需求不足及传统设计建造流程的改变是当前CLT建筑在我国发展推广所面临的主要障碍,但我国在CLT厂商及项目的市场基础、国产树种CLT的研发应用、政策法规的引导支持等方面正在逐步发展完善,未来将具有较大的市场空间和可行的发展路径。     

“C”型平面高层结构设计分析与调整措施探讨

为研究平面凹凸特别不规则以及结构扭转、楼层抗剪承载力一般性不规则结构的受力性能,采用PKPM-SATWE软件建立模型并进行计算分析.结果表明,结构楼层质量分布均匀,结构刚度分布合理,不存在薄弱层,结构剪重比满足规范要求,在规定风荷载（100a一遇）及地震作用下存在一定超出规范一般限值要求项,但均满足较为严格的规定要求;为降低平面不规则给结构所带来的不利影响,可采取提高框架柱抗震等级、增加楼板配筋和增加结构薄弱层剪力墙及框架柱的配筋三种措施进行调整.     

基于换算长细比的正交胶合木稳定系数计算方法

正交胶合木(CLT)纵横向层板交叉组坯,纵向层板强度和模量较高,横向层板强度和模量较低,其截面呈强弱相间的条带状结构.当轴心受压构件失稳时,截面剪切变形对CLT稳定承载力的影响不可忽略,故不能采用一般木产品的稳定承载力计算方法.目前我国相关标准中尚无CLT轴心受压构件稳定承载力计算方法.鉴于此,从CLT产品的截面构成特...     

Evaluating rolling shear strength properties of cross-laminated timber by short-span bending tests and modified planar shear tests

This paper presents an experimental study on rolling shear (RS) strength properties of non-edge-glued cross-laminated timber (CLT) made out of New Zealand Radiata pine (Pinus radiata) structural timber. CLT specimens with 35 and 20 mm thick laminations were studied to evaluate the influence of lamination thickness on the RS strength of CLT. Short-span three-point bending tests were used to introduce high RS stresses in cross layers of CLT specimens and facilitate the RS failure mechanism. Modified planar shear tests from the conventional two-plate planar shear tests were also used to evaluate the RS strength properties. It was found that two test methods yielded comparable RS strength properties and the lamination thickness significantly affected RS strength of the CLT specimens. The test results also indicated that the recommended characteristic RS strength values of CLT products in Europe and Canada might be over conservative. Also, it might be more efficient to specify different RS strength values for CLT with different lamination thickness given the minimum width-to-depth ratio of laminations is satisfied.     

各种房屋抗震能力的比较

近年多发较大地震,对国民的生活和国家的经济建设造成很大的负面影响,与此同时地震对建筑物的抗震能力也提出了更高要求。本文通过几种不同结构形式抗震能力的比较,得出钢结构抗震能力最强,剪力墙结构次之等不同结论,可供设计人员参考。     

地震中柜类家具防倾翻设计

柜类家具在地震中产生震害的危害性大。在我国引起家具震害的中小地震频发,但家具震害的相关研究较少。对柜类家具在地震作用下的摇晃现象进行运动理论分析,运用数值模拟研究方法结合柜体倾翻试验,对影响地震中柜体倾翻的自身因素进行研究,用于后续指导柜类家具的防倾翻设计。结果表明:在相同地震力大小的条件下,柜体倾翻的时间会受到柜体重心深度和高度变化的影响。当地震力大小不足以克服柜脚与地面间的摩擦力时,柜体重心的深度和高度是影响柜体倾翻的主要因素;柜体倾翻时间与柜体重心的深度成正比,与柜体重心的高度成反比;当柜体深高比相同时,倾翻时间与柜体侧面体量成正比;柜体倾翻试验验证了数值模拟研究方法,具有可行性和可靠性,可用于后续柜类家具安全尺寸的设计。     

Use of wood products in multi-storey residential buildings: views of Swedish actors and suggested measures for an increased use

ABSTRACT

Many studies have shown that wooden buildings in general have a lower climate impact than buildings built of conventional materials such as concrete and steel. In Sweden, however, only about 10% of the multi-dwelling buildings are built with timber frames. The goal of this empirical study is to provide a broad picture of the views of Swedish actors regarding the use of wood products in multi-storey residential buildings and suggest measures for an increased use. A questionnaire concerning the use of wood products in construction was sent out to Swedish developers, main contractors, and architects and 100 answers were received. The study shows that the views of the groups of actors differ in some respects and factors that may either facilitate or be obstacles to an increased use of wood products were identified and discussed.     

中国与日本建筑结构用定向刨花板标准对比研究

近年来我国定向刨花板（OSB）产能逐年增加,目前主要应用于家具制造与装修,而在建筑结构中应用相对较少;为了实现我国碳达峰、碳中和目标,随着村镇装配式建筑的发展,建筑结构用OSB使用量必将大幅上升,主要用作木结构和轻钢建筑的墙面板、楼面板和屋面板等结构用覆面板。1987年日本就制定了日本农林标准（JAS）《構造用パネル》（《结构用人造板》,最新版JAS 0360:2019）,作为结构用OSB产品质量认证和检测的主要依据,而我国目前没有专用的结构用OSB产品标准。与结构用OSB 日本农林标准比较,我国行业标准LY/T 1580-2010《定向刨花板》中规定的承载型板材在指标要求、试件尺寸和数量、试验方法、抽样方案以及产品合格判定方法等方面存在较大差异。通过对比中日标准技术规定的异同,以期为OSB在我国建筑结构领域使用的规范化与标准化提供参考。鉴于钉连接性能对建筑结构的抗震性能影响显著,建议在我国标准修订中增加该项指标规定。     

国外木结构建筑的抗震性能研究

根据国外的有关文献资料，论述了影响木框架结构抗震性能的主要因素以及木框架建筑的震害调查结果，介绍了目前木框架建筑抗震研究的最新成果。     

木结构榫卯节点抗震性能及震后加固修复研究进展

总结了国内外有关传统木结构常用榫卯节点抗震性能的研究进展,主要包括直榫连接与燕尾榫连接,同时介绍了扁钢、马口铁与碳纤维布三种木结构榫卯节点加固修复方法的相关研究成果,并对今后进一步研究提出建议,以期为木结构建筑震后加固与修复及我国古木建筑保护提供参考。     

体育馆用木质地板

阐述体育馆用木质地板应具备的基本特性和DIN 18032-2中所规定的六项主要功能指标,介绍体育馆用木地板的主要结构类型,为我国体育馆用木质地板的研究、设计、制造、铺装和应用提供参考。     

Multi-storey timber construction and bioeconomy – barriers and opportunities

Multi-storey timber construction has been developed and promoted in Finland since the 1990s. Despite these efforts, the share of timber frames in multi-storey construction has remained very low. Construction business is also very resource intensive and accounts for a large share of greenhouse gas emissions. Increasing the use of renewable materials, mainly wood, in buildings, could make construction more sustainable and a part of bioeconomy. This study aimed at identifying barriers to the adoption of multi-storey timber construction, ways in which wood could compete with established solutions and possibilities for partly integrating construction into bioeconomy. Based on 18 interviews of representatives from the entire value chain, this study presents insights into introducing new solutions into a conservative field. Our results indicate that multi-storey timber construction could offer competitive solutions for more sustainable construction, even though barriers to its adoption still exist.     

Reliability analysis and duration-of-load strength adjustment factor of the rolling shear strength of cross laminated timber

In this study, the duration-of-load effect on the rolling shear strength of cross laminated timber (CLT), with different cross-sectional layups (five-layer and three-layer), was evaluated. A stress-based damage accumulation model is chosen to evaluate the duration-of-load strength adjustment factor of the rolling shear strength of CLT. This model incorporates the established short-term rolling shear strength of material and predicts the time to failure under arbitrary loading history. The model has been calibrated and verified based on the test data from low cycle trapezoidal fatigue tests (damage accumulation tests) in the previous study. The long-term rolling shear behaviour of CLT can then be evaluated from this verified model. As the developed damage accumulation model is a probabilistic model, it can be incorporated into a time based reliability assessment of the CLT products, considering short-term, snow, and dead load only loading cases. The reliability analysis results and factors reflecting the duration-of-load effect on the rolling shear strength of CLT are compared and discussed. The characteristic of this modeling theory lies in that the verified model is also able to predict the duration-of-load behaviour of CLT products under arbitrary loading history, such as long-term dead load case; then, these predictions of time to failure from the damage accumulation model can elucidate duration of load by the stress ratio evaluation approach. The results suggest that the duration-of-load rolling shear strength adjustment factor for CLT is more severe than the general duration-of-load adjustment factor for lumber; this difference should be considered in the introduction of CLT into the building codes for engineered wood design.     

同基础有偏心多塔基底隔震结构的隔震效果分析

对有偏心的单塔基底隔震结构和同基础多塔基底隔震结构进行数值分析，计算结果表明，对有偏心的单塔隔震结构，在地震作用下采用同基础多塔基底隔震结构的形式能大幅度降低结构的扭转反应，因此，条件许可时相邻偏心结构的建筑，采用同基础隔震的形式，对提高隔震效果是有利的。     

夏热冬冷地区近零能耗住宅围护结构性能优化方法研究

为探究围护结构性能对夏热冬冷地区低密度住宅能耗的影响,通过建立低密度住宅基准模型,从近零能耗技术标准中提炼出了夏热冬冷地区围护结构参数取值范围。利用参数化平台和遗传算法进行了建模和分析,得出了能耗需求达到最低值时,建筑4个朝向窗墙比、外墙传热系数、屋面传热系数、外窗传热系数、外窗得热系数这8个变量或影响因子的取值情况和变化规律。采用的研究方法和研究路线对于其他类型建筑(如商场,医院,办公楼等)的围护结构性能优化设计具有一定的参考价值和指导意义。     

Load sharing and weakest lamina effects on the compressive resistance of cross-laminated timber under in-plane loading

A new approach was developed to predict the compressive resistance of cross-laminated timber (CLT) using the compressive strength of small samples of different grade lamina from E12 and E8 larch, and E10 and E6 nut pine. CLT of three different thicknesses was manufactured using different grades of laminas from each species. To evaluate the compressive resistance of CLT, three different methods were employed. The first method was used to determine the compressive resistance, which was predicted by multiplying the compressive strength of lamina aligned with the loading direction, and the cross-sectional areas of the lamina. The second method is similar to the first method, but additionally considering the stiffness ratio of the laminas. The third method developed from the current study accounts for load sharing and weakest lamina effects in the prediction of compressive resistance. When the lower 5th percentile compressive resistance in a major direction was predicted using the first two methods, the difference between the experimental test and the predicted value ranged from 2.5 to 43.4%. However, when the compressive resistance in a major direction was predicted using the developed method from the current study, the difference between the experimental test and predicted value ranged from ??8.7 to 10.8%.