Protecting a Cemetery in Saqqara: Site Works 1975–2009

Abstract

This article considers the varied threats to Ancient Egyptian architectural remains that have been exposed by modern excavation. A number of possible measures that counter such threats are outlined, together with the practical difficulties facing the architectural conservator working in this context. The approach taken at the New Kingdom Necropolis in Saqqara — a group of elite tombs constructed c. 1350–1250 BC — during the post-excavation phase is detailed, with an emphasis on the works carried out by the author from 2004 to 2009. This encompasses the conservation of surviving limestone relief decoration in situ, the reconstruction of missing masonry elements, and the final presentation of the site to visitors.     

Chemical composition of architectural plaster at the Classic Maya kingdom of Piedras Negras,Guatemala

Architectural plaster from elite masonry structures at the Classic Maya kingdom of Piedras Negras, Guatemala, is examined. Chemical composition is determined through X-ray fluorescence and compared statistically. Based on this sample, it was observed that any single masonry building was coated with plaster made from a single source of limestone and limestone-based aggregate, but that architectural plaster from different buildings across the site varied in chemical composition. It is concluded that this pattern is best accounted for by a model of rotational labor obligations to the state, with spatially distinct groups being responsible for manufacturing plaster for specific buildings.     

THE ROMANESQUE FRIEZE AT LINCOLN CATHEDRAL (ENGLAND)—PRIMARY OR SECONDARY INSERTION? MAGNETIC CONSIDERATIONS*

The current debate about the age of the Romanesque frieze of Lincoln Cathedral weighs archaeological evidence against art history. On the one hand, the panels appear to be an integral part of the original Norman structure built by the first bishop (AD 1072–92). However, on grounds of style and artistic comparisons, art historians argue for a later installation during the restoration of AD 1141–6. In order to determine when the panels were stabilized in the cathedral, we used a new method that measures their degree of remagnetization by the earth's magnetic field since they were quarried. The longer that masonry remains stabilized in a given orientation, the greater its viscous remagnetization. Viscous remanent magnetization dating has previously been successful with this particular type of limestone masonry. Our results lend support to the view that the panels were installed in the early 1140s.     

WHO INVENTED THE CLAW CHISEL?

Summary. Part I discusses the problem of the introduction of the claw chisel in stone masonry and sculpture. This tool was thought to have been invented in 6th-century Greece for the needs of marble carving. The detection of its traces on a tomb of 7th-century Egypt in soft limestone, however, now suggests not only that the Greeks borrowed it from the Egyptians but also that it was not originally a marbleworker's tool. Part II deals with both the tomb and career of an Egyptian official designated Nespeqashuty D in order to place into a chronological framework one of the earliest securely dated attestations for the use of the claw chisel in Egyptian art. Both parts are intended to place the impact of Egypt on Greece into sharper focus.     

Assessment of Multi-Wythe Stone Masonry Subjected to Seismic Hazards

Heritage stone buildings are typically vulnerable to seismic events. Results of an experimental program were analyzed to evaluate the shear strength and intrinsic damping of stone masonry representative of the West Block of the Canadian Parliamentary Precinct in Ottawa. Eight representative wall specimens with different rehabilitation schemes had been tested under different static and dynamic loadings. Each wall had wythes of sandstone and limestone connected by a rubble core. The results show the shear strength of the walls could be predicted accurately and that no strengthening scheme was particularly beneficial. The effective viscous damping ratios varied between 7 and 9%.     

In the Steps of William the Conqueror: Neutron Activation Analysis of Caen Stone*

Quarries in the Bathonian stone formation surrounding Caen produced high‐quality limestone for medieval churches in northern France and southern England and for their sculptural decoration. To investigate compositional differences among proximate stone sources, 103 samples collected from five separate quarries were analysed by NAA. The results show Caen stone to be essentially pure calcite and relatively homogeneous, but distinction among quarries is possible by discriminant analysis. Comparing compositions of quarry samples with data in the Brookhaven Limestone Database identified the origin of stone used in masonry and sculpture at Saint‐Étienne and La Trinité, Caen, and in several museum objects.     

A Procedure to Investigate the Collapse Behavior of Masonry Domes: Some Meaningful Cases

Masonry domes represent an important part of the architectural heritage. However, the literature about domes analysis seems less consistent than that referred to other masonry structures. The collapses that have happened in recent years as a consequence of seismic actions or lack of maintenance show the need for detailed studies. Here a limit analysis to evaluate the masonry domes behavior is presented. An algorithm based on the kinematic approach has been developed to evaluate the geometric position of the hinges that determine the minimum collapse load multiplier. The proposed procedure is validated by a comparison with some meaningful cases—the collapse of Anime Sante Church in L’Aquila, the collapse of San Nicolò Cathedral in Noto, the crack pattern of San Carlo Alle Quattro Fontane Church in Rome, and the analysis developed on Hagia Sofia in Istanbul. The comparison with real cases shows a good agreement between the model results and the phenomenological crack patterns.     

Seismic Analysis of Masonry Gravity Dams Using the Discrete Element Method: Implementation and Application

Much research in recent years has focused on the seismic analysis of concrete and earthfill dams, and few works have addressed the case of masonry dams. The structural behavior of masonry dams is controlled essentially by its discontinuous nature, which may induce significant nonlinear response during an intense earthquake. In this article, a numerical tool based on the Discrete Element Method is presented, aimed at the static, dynamic, and hydromechanical analysis of masonry gravity dams. The use of discontinuous models is mandatory for the study of failure mechanisms involving the masonry discontinuities, the dam-rock interface or the rock mass joints. The Discrete Element Method is able to assemble continuous and discontinuous meshes simultaneously in the same model, providing a versatile tool to consider various assumptions and levels of analysis, ranging from simplified to detailed structural representations. A comprehensive study of the seismic behavior of Lagoa Comprida Dam, located in Portugal, is presented. Both continuous and discontinuous models were developed to assess the main failure mechanisms, including overstress, partial and global sliding, and overturning.     

Red Blood Cell Haemotaphonomy of Experimental Human Bloodstains on Techno-Prehistoric Lithic Raw Materials

Mammalian erythrocytes or red blood cells (RBC)—whose presence in a smear is evidence for blood residues—have been previously reported on prehistoric implements estimated to be approximately two million years old. On the basis of the Principle of Actualism, bloodstains from modern human individuals were obtained on obsidian, limestone and chert. Then, they were stored in a unsterile room under microclimatically unmanipulated fluctuating conditions, for lengths of time ranging from 7 years, 6 months to 10 years, 2 months. Afterwards, the bloodstains were coated with both carbon and gold and then examined by a JEOL JSM-6400 scanning electron microscope (SEM). Results revealed a time-independent preservation of erythrocyte integrity, displaying moon-like shapes, and negative replicas. These results agree with several previously reported SEM analyses of younger mammalian bloodstains on chert and materials other than obsidian and limestone, and lead to consider the moon-like shapes (hecatocytes, a term ex novo) and negative replicas (janocytes, another term ex novo) as the genuine RBC morphologies characteristic of (at least mammalian) bloodstains.     

The afterlife of earthen-core buildings: A taphonomic study of threatened and effaced architecture in Central Belize

Buried architecture poses an interpretive challenge to field archaeologists the world over. The depositional sequence of the site must be reconstructed through excavation and stratigraphic analysis, and the various phases of construction and use that occurred in the past must be inferred. Effaced earthen-core architecture (e.g., architecture that was once faced with a masonry outer layer that is no longer present) constitutes a heightened challenge in this regard, as events and layers are not always clearly distinguishable, an interpretive difficulty that can be compounded when such architecture is threatened and decay accelerated by modern-day land use activities such as bulldozing and plowing. The case study presented here focuses on an ancient Maya E-Group architectural configuration—a triangular arrangement of structures that served to commemorate astronomical events, among other functions—that is being degraded through repetitive plowing. The significance of this site in regard to Maya archaeology is undeniable, as it was used and reused over a period of at least eight centuries. The site warranted a salvage-based approach designed to gather maximal quantities and types of data when only a minimal amount of time, labor, and funding was available. The procedure presented here was developed for a specific example of endangered, earthen-core Maya architecture in Belize; however, it is applicable to any archaeological project that faces similar obstacles in examining and documenting architecture before it is either eroded or intentionally destroyed.     

Performance of Structures in the Mw 6.1 Mae Lao Earthquake in Thailand on May 5, 2014 and Implications for Future Construction

An M_w 6.1 earthquake struck northern Thailand on the 5^th of May 2014. The epicenter was located near Mae Lao district in Chiang Rai province. The earthquake caused unprecedented damage to structures, the most damaging earthquake ever in recorded Thai history. Five hundred and ninety-four buildings out of 10,863 were damaged to the extent that they were unsafe for occupancy. This article presents a reconnaissance investigation of damage to buildings and bridges in the two districts—Phan and Mae Lao—which suffered the most damage. Attention is paid to the performance of buildings with similar configurations and structural design, but with different layout of unreinforced masonry infills as non-structural components.     

故宫灵沼轩风振响应分析

故宫灵沼轩是一座砌体结构与钢结构组合而成的文物建筑。为有效对其保护,采用数值模拟方法,研究了风振作用下结构的动力响应。基于灵沼轩结构现状,建立了有限元模型。通过模态分析,获得了灵沼轩的基频和主振型;通过对结构施加y向脉动风荷载,研究了重现期为50年时结构的风振特性,评价了结构在风荷载作用下的安全现状。结果表明:灵沼轩结构基频为f=5.75Hz,在x及y向的主振型以局部振动为主;脉动风压作用下,结构保持稳定振动状态,但顶部位置加速度峰值偏大。另风压作用下,砌体结构部分位置的抗拉强度不足,应在日常维护中予以重视;钢结构部分由于材料强度大,因而不会出现强度破坏。     

Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (VI): Discrete Element Approach

ABSTRACT

Although many experimental tests and numerical models are available in the literature, the numerical simulation of the seismic response of existing masonry buildings is still a challenging problem. While the nonlinear behavior of masonry structures is reasonably predictable when the out-of-plane behavior can be considered inhibited, when the in-plane and out-of-plane responses coexist and interact, simplified models seem unable to provide reliable numerical predictions. In this article, taking advantage of the experimental tests carried out in a shaking table on two masonry prototypes at LNEC, a macro-element approach is applied for the numerical simulations of their nonlinear response. The adopted approach allows simulating the nonlinear behavior of masonry structures considering the in-plane and out-of-plane responses. Since it is based on a simple mechanical scheme, explicitly oriented to representing the main failure mechanisms of masonry, its computational cost is greatly reduced with respect to rigorous solutions, namely nonlinear FEM approaches. Two modeling strategies are adopted, namely a regular mesh independent from the real texture of the prototypes and a detailed one coherent with the units disposal. The numerical results are discussed and the correlation between the nonlinear static analyses and the dynamic response is provided.     

Reconstruction of the Rib Vaults of the Hypostyle Hall in the Maniace Castle of Siracusa After the 1693 Earthquake

Built in the first half of the 13th century on behalf of the Emperor Frederick II, the Maniace Castle of Siracusa focuses its enigma in the hypostyle hall (which was composed of 25 quadripartite rib vaults) and the design criteria adopted for its implementation. Recent research and a careful rereading of the documentary “restoration project” after the earthquake of 1693 have offered new tools to understand the construction techniques and building procedures for the entire organism. It has been possible to demonstrate that the different material (white limestone and volcanic stone) used for the vaults is, in fact, a product of reconstruction. The constructive node, which historiography has taken for granted, is now crucial—the documentary evidence of the restoration after the earthquake compared with the materials found in situ provide interpretive keys to decode genesis and procedures of the huge structure built five centuries before.     

Decay of Limestone Statues at Mount Nemrut (Adiyaman,Turkey)

Mount Nemrut is a 2,206 m high mountain located in Adiyaman, Turkey. A number of monumental statues, a 50-m high tumulus, and a lion horoscope were constructed at the top of the mountain by King Antiochos I (69–36 bc) of the Commagene Kingdom. The site was included in the UNESCO World Heritage List in 1987 due to its unique character. However, the limestone statues located on both the east and the west terraces of the site are getting deteriorated. This study investigates the weathering of the limestone at Mount Nemrut based on field and laboratory studies. It is found that the dissolution occurs along microcracks developed in the limestone during geological time. It is more pronounced in the east terrace where freezing-thawing cycles are more than the west terrace. Furthermore, dissolution is more effective for the faces of the statues exposed to direct atmospheric contact. Due to harsh atmospheric conditions with dominant wetting-drying and freezing-thawing processes at the site, it is recommended that direct rain and snow contact with the statues should be minimized.     

Calcareous nannofossils in medieval mortar and mortar‐based materials: A powerful tool for provenance analysis

Calcareous nannofossils—very small‐scaled marine microfossils—occur in many archaeological materials. Foremost, these include limestones used in masonry, material which has not experienced significant modification by humans. Poorly documented are nannofossils in mortars, because the burning process of quicklime requires the heating of the raw material to > 800°C. Here we focus on calcareous nannofossils in mortar and mortar‐based samples of four medieval buildings in northern Germany. The study documents the presence of nannofossils in historic mortars. It supplies evidence for the provenance of the mortars used, thereby introducing a new tool for mortar provenance studies.     

Effect of stereotomy on the lower bound value of minimum thickness of semi-circular masonry arches

Constructing structural systems with the minimal required cross section of its members was a strong motivation for progress whole along the history of building. This article investigates the effect of stereotomy on the minimum thickness value of a semi-circular arch made of masonry: a material with negligible tensile strength. The arch is modeled with its center line to which the loading is assigned according to arch length. Here, instead of some scalar parameters such as the rupture angle and the location of the middle hinge on the intrados, the geometry of the stereotomy is associated with a continuous function. Stereotomy-related constraints are introduced to keep the results feasible from an engineering point of view, and it is also demonstrated that they are essential for a well-posed constrained optimization problem. The necessary condition for a non-vanishing lower bound of minimum thickness values is derived analytically considering the assumptions of limit state analysis, infinite friction, and a no-tension material model. The lower bound thickness to radius ratio (t/R) is found to be t/R = 0.0819. A numerical method is introduced to demonstrate the existence of a valid stereotomy at the lower bound. Multiple admissible stereotomy patterns are presented at various minimum thickness values (higher than the lower bound) to demonstrate that suitable stereotomy for a fixed (t/R) ratio is far not unique—in general even the location of the middle hinge and the rupture angle might vary.     

Determination of Shear Strength of Masonry Panels Through Different Tests

This study addresses the problem of evaluation of strength of masonry walls. In-plane behavior of masonry panels has been studied under monotonic diagonal-compression and shear-compression loading in quasi-static test facility. The results of 35 laboratory and in situ tests are analyzed to show that in the case of the diagonal compression test results are lower than the strength of masonry walls evaluated trough the shear-compression test, highlighting the problem of choosing the test which best simulates to the real behavior of the masonry when stressed by lateral loads. A presentation is also given of the results of a F.E. investigation for shear strength evaluation of masonry walls. F.E. modeling non-linear procedure was used for the representation of masonry panels. The numerical simulations are compared with experimental results and the reliability of the different finite element models is discussed, thus confirming the different shear strength values measured in the experimental campaign.     

Source Modeling of the Kozani and Arnea 1995 Events with Strong Motion Estimates for the City of Thessaloniki

In Turkey, with the occurrence of almost every strong and even moderate earthquake, damage to masonry minarets is observed. In the present work, efficiency of vertical post-tensioning application to reinforce masonry minarets against earthquakes has been investigated. Considering a representative minaret and its post-tensioned counterpart, and performing spectral and time-history analyses, the effects of post-tensioning on the axial stresses, top lateral displacements and overturning safety have been determined. Obtained results have shown that vertical post-tensioning application is a very efficient method to reduce axial tensile stresses and lateral displacements, and to assure the overturning safety of masonry minarets against earthquakes.