An experimental micromorphological investigation of bedding construction in the Middle Stone Age of Sibudu,South Africa

We conducted experiments to compare the micromorphological signatures of modern burnt sedge and grass bedding to laminated layers of carbonized material and phytoliths in Middle Stone Age deposits at the shelter, Sibudu. The experiments were designed to clarify the formation processes associated with the laminated layers and to investigate whether these previously identified layers of bedding were deliberately burned or not. The results indicate that the laminated layers were most likely produced by human activity related to the construction, maintenance and burning of bedding. Furthermore, our experiments demonstrate that large volumes of vegetal material could have produced the relatively thin, archaeological deposits of burnt bedding.     

The ‘invisible’ hearths: a contribution to the discernment of Mesolithic non-structured surface hearths

In the cover sand area of the NW European plain very little is known about fireplaces within Mesolithic settlement areas. Yet the frequent occurrence of burnt ecofacts (hazelnut shells and bone) and artefacts (flint and quartzite) clearly indicates the presence of (surface) hearths on nearly every campsite. Most of these hearths are non-structured and are thus barely visible in the soil. Furthermore in most spatial studies minimal effort has been made to locate these ‘invisible’ hearths as accurately as possible. This paper discusses the potential and modalities of detailed spatial analysis of burnt artefacts and ecofacts, using recently obtained archaeological and experimental evidences. It is concluded that such an analysis can offer interesting insights into the dynamics of Mesolithic hearths.     

Experimental insights into alternative strategies of lithic heat treatment

Conditions in which thermal fractures occur are explored experimentally, and the results are used to assess heat treatment strategies. We conclude that no single ‘critical temperature’ for thermal fracturing or heat treatment can be specified for any particular raw material, as has so often been attempted, because threshold temperatures exist in relationship to specimen sizes. Our experiments show that smaller specimens are resilient to greater ranges of temperature fluctuations than larger ones, and that by manufacturing/selecting specimens of smaller sizes there is more potential to heat them rapidly and to higher temperatures without producing thermal fractures. We hypothesize a continuum of heat treating strategies between a ‘slow and steady’ strategy, which has overwhelmingly dominated past experimental designs, and a ‘fast’ strategy, which has received much less attention. The paper discusses the economic and technological contexts to which different heat treating strategies might be suited.     

Im Blickwinkel der Technik: Neue Verhältnisse von Wissenschaftstheorie und Wissenschaftsgeschichte

Changing Perspectives – From the Experimental to the Technological Turn in History and Philosophy of Science. In the 1960s the philosophy of science was transformed through the encounter with the history of science, resulting in a collaborative venture by the name of “History and Philosophy of Science” (HPS). Philosophy of science adopted ever more regularly the format of the case study to reconstruct certain episodes from the history of science, and historians were mostly interested in the production of scientific knowledge. The so‐called “experimental turn” of the 1980s owed to this interaction between philosophy and history. Its guiding question remained quite traditional, however, namely “How do the sciences achieve an agreement between representation and reality?” Only the answers to this question broke with tradition by focusing not on theory but on the role of instruments and experiments. – Roughly 30 years after the experimental turn, another transformative encounter appears to be taking place. HPS is being transformed in the encounter with philosophy of technology. From the point of view of philosophy of technology, the question does not arise whether and how the agreement of mind and world, representation and reality can be achieved. When things are constructed, built or made, human thinking and physical materiality are inseparably intertwined. Instead of seeking to describe a mind‐independent reality, technoscientific researchers are working to acquire and demonstrate capabilities of experimental or predictive control. When science is regarded as a kind of technology, a program of study opens up for epistemology and so do avenues for the historiography of science. History of science might now show how the problems and procedures of the sciences arise from and impinge back upon a world that is itself a product of science and technology. It thereby abandons its traditional HPS niche existence and joins forces with environmental history, history of technology, social, labor, and consumer history.     

Identifying grinding,scoring and rubbing use-wear on experimental ochre pieces

Ochre pieces were used experimentally for a variety of grinding, scoring and rubbing activities to record and compare the use-wear markings that each activity creates on the ochre piece. Ochre that is ground on coarse or fine-grained slabs develops parallel striations that cover the surface of the piece. The striations have unfrayed ends. Grinding is the only activity that results in significant changes to the surface shape of the ochre, producing a plane. When ochre is scored either to create a deliberate design or to produce powder, the grooves that form often do not reach all the edges of the used surface and they regularly have frayed terminations. This demonstrates that the incisions were created by multiple scoring strokes. When ochre is scored to manufacture ochre powder the incisions that are generated are parallel groups of grooves with erratically oriented grooves as well. Bone and wooden tools are soft and they therefore do not generally create obvious incisions on ochre pieces. Grooves created through grinding on a slab or scoring with a stone tool have microstriations within them and they show a range of profile shapes. The most common use-wear from rubbing ochre on animal hide, human skin, human hair and wood is smoothing, edge rounding and polish, although incisions and microstriations also occur occasionally. Residues are often left on an ochre piece after rubbing or scoring with organic materials. The comparative collection of macro- and microscopic use-wear marks from experimentally ground, scored and rubbed ochre is useful as an aid to classifying archaeological collections of ochre.     

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.     

Rocking Behavior of Irregular Free-Standing Objects Subjected to Earthquake Motion

Free-standing rigid objects and structures are dominantly found to exhibit rocking behavior and can be vulnerable to overturning during an earthquake as demonstrated by numerous past earthquake events. Such objects are typically considered to be displacement sensitive with their rocking response being well presented by the Peak Displacement Demand (PDD) parameter of the supporting floor’s motion. This in turn can be directly related to an object’s width (along the direction of motion) for assessing its vulnerability to overturn. Such findings have been sufficiently justified by refined dynamic analysis supported by experimental evaluations which were based on rigid blocks with uniform geometric format (i.e., regular in their mass distribution). However, vulnerable rocking objects can be asymmetric and accordingly their sensitivity to floor displacement cannot be directly related to their width. The key parameter which defines irregular objects’ response to rocking motion is represented by the degree of eccentricity of their center of mass. In this study, the well-known rocking equation of motion is reconfigured and devised to model the rocking responses for 280 irregular objects undergoing eight earthquake motions which included artificial and recorded earthquakes. Analytical results obtained from solving the adjusted equation of motion were evaluated with sophisticated finite element (FE) models simulating the 280 irregular cases. This experimentally validated FE modeling approach was found to be time- and cost-effective for understating the rocking behavior of asymmetric objects as well as clarifying an interesting relationship between the object’s damping level and the condition of the supporting base (i.e., whether being provided with supports at the points of rotation or not). The rocking response of irregular objects was found to be highly influenced by the level of eccentricity of the object when excited by motions with high displacement amplitudes, while such influence was not found noticeable by wider objects. Based on the developed trends between the maximum top displacement of irregular objects and the PDD, an expression for estimating the rocking amplitudes is proposed which is a function of the object’s eccentricity.     

不同方法加固古建筑榫卯构架抗震试验

为保护古建筑,采用试验方法,研究了不同方法加固榫卯节点后木构架的抗震性能。基于故宫太和殿某开间梁柱节点的具体尺寸,制作了1:8比例的4梁4柱木结构空间框架模型,其中梁和柱考虑为燕尾榫形式连接。采用人工加载方式,进行了低周反复加载试验,研究了马口铁、CFRP布和钢构件加固榫卯节点后对木构架抗震性能的影响。基于试验结果,获得了加固前后构架的力-侧移滞回曲线和骨架曲线,分析了构架耗能能力、刚度退化规律及变形能力,对不同方法加固木构架的抗震效果进行了对比,对其工程应用提出了建议。     

Experimental Study on Seismically Resilient Two-Span Bridge Models Designed for Disassembly

Shake-table studies were conducted on a ¼-scale, 2-span bridge model incorporating a newly-developed concept of replaceable plastic hinges and columns that can be easily assembled and disassembled. The plastic hinges incorporate novel materials that mitigate column damage and permanent drift, allowing the bridge to undergo intense seismic shaking and remain operational when most conventional bridges would warrant demolition. Designed to be disassembled, the column components have the potential to be reused, which is intended to help mitigate the environmental impact from material extraction and manufacture. The concept feasibility was demonstrated by assembling, testing, and disassembling the same bridge model twice.     

Liquefaction-Induced Lateral Load on Pile in a Medium Dr Sand Layer

One-g shake-table experiments are conducted to explore the response of single piles due to liquefaction-induced lateral soil flow. The piles are embedded in saturated Medium Relative Density (Dr) sand strata 1.7–5.0 m in thickness. Peak lateral pile displacements and bending moments are recorded and analyzed by uniform and triangular pressure distributions. On this basis, the observed levels of pile bending moment upon liquefaction suggest a hydrostatic lateral pressure approximately equal to that due to the total overburden stress. Using the experimental data, comparisons with current recommendations are made, and the Showa Bridge case history is briefly assessed.