The increasing costs of the conventional building materials, such as concrete and steel, led to the dependence on junk and scrap to build houses in poor communities in Egypt. The governmental efforts to solve the problem of this informal construction trend require long-term financial support that is not guaranteed under the circumstances of the high inflation rate and the global economic crisis. Exploring natural building materials and local building materials in a society provides a new chance in the local development that is driven from the inside. Mudbrick is one of the common building materials used to build houses in the rural communities, and famous architects have tried to revive this history (Fathy, 1993). Lately, more attention has been paid to agricultural residues to be the new building material that solves the problem of the decrease of the soil fertility that is required to make the mudbricks (Kennedy, 2004). One of the most abundant residues in Egypt and the Middle East is Date Palm Rachis (Elmously, 2005).

The dried date palm parts and the date palm main components are illustrated in Figure 1 and Figure 2.

Date palm rachis has been used as a building material in rural areas in Egypt and the Middle East. This technical heritage has accumulated over centuries due to the abundance of the highly renewable date palm rachis, as date palm rachis is the most available pruning residues of Date Palm Trees that cover the vast area of the deserts, oases and the Nile Valley, as shown in Table 1 (Elmously, 2005).

Traditionally, rural houses, eco-lodges and public places combined date palm rachis and date palm trunks to build roofs. In Sinai, date palm rachis is accumulated in layers to make exterior sheathing for the roofs with thicknesses that exceeds 20 cm to shield the houses from the direct sunlight, as illustrated in Figure 3 (Ibrahim, 2010). In Siwa and the western oases, date palm trunks are halved and used as ceiling beams, where Date Palm Rachis is used as a sheathing material that will enhance the interior design of the ceiling, as illustrated in Figure 4 (Alamuddine, 2001). In temporary structures in the Nile valley such as shades, date palm rachis is threaded to make walls and roofs that are fastened to small tree stems which work as columns and beams in the corners (Unknown Author, 2001).

This increasing dependence on date palm rachis as a structural material led to previous research that push the limits of date palm rachis as an independent structural material to build cheap and fast shades. These experiments depended solely on building full scale mock-ups of the proposed shades due to the lack of mechanical properties of palm rachis that are required for the structural analysis, although this could help to expect static loads, wind, seismic loads and the limits of the spans of the proposed structures. The first pioneering experiment was based on a proposal of gathering date palm rachis as bundles that are formed as arches. Those arches were planted in the wet soil at spacing of 5m, while covering a span of 13m. As revolutionary as it sounds, the structure succeeded in covering the span, but only after using palm trunks as intermediate columns along every arch on intervals of 3.25 m. Hence, the onsite decision led to construct a shade with a span that is actually only 3.25 m (Error processing citation, n.d.). Figure 7 pictures the vault during construction, while Figure 8 illustrates the interior columns that were closely spaced. The connection used was rope-based connection (Figure 9).

Another experiment using date palm rachis to build shades was based on the structural concept of ring beams.

Date palm rachis were gathered to make curved bundles that are planted along the parameter of the proposed circle to cover. Then, a plywood ring was made to attach the edges of the curved bundles. However, the height of the structure decreased due to the deflection that happened under the weight of the final sheathing, as illustrated in Figure 10 to Figure 12 (”Turn Over a New Leaf”, 2013).

Therefore, it can be concluded from the previous literature review, that building shades using date palm rachis while depending solely on building real mock-ups is not sufficient to predict onsite behavior and unexpected loads such as sheathing weight, wind and seismic loads. Therefore, this paper aims to introduce the closest estimation of the mechanical properties of date palm rachis, according to the natural variations of date palm rachis and the available equipment in the laboratories of Faculty of Engineering, Ain Shams University.

Previous research showed that the properties of date palm rachis are competitive to imported wood species, specifically those of spruce wood (Unknown Author, 2001). However, due to the complexity of the variable nature of date palm rachis, those previous studies only measured some of the longitudinal properties for the whole date palm rachis regardless of the other two dimensions, as date palm rachis is considered an anisotropic material (Figure 13).

In nature, materials are classified into isotropic, orthotropic, and anisotropic materials. Isotropic materials are the materials where the mechanical properties are identical in all directions, such as glass and metals. On the other hand, the properties of fibrous materials such as timber vary according to the fiberds’ direction, which makes them anisotropic materials (Mascia, & Lahr, 2006). However, in engineering elastic models timber is considered an orthotropic material.

The linear orthotropic model suggests three planes of symmetry in the following three directions: longitudinal, radial and tangential, which are coincident with the three Cartesian directions: x, y and z. Where longitudinal direction of timber is parallel to the fibers, the radial direction is perpendicular to the fibers and the growth rings and the tangential direction is perpendicular to the fibers and tangential to the growth rings (Green et al., 2010). Accordingly, if date palm rachis is to be defined as an orthotropic material, the properties in the tangential and radial directions are identical due to the lack of growth rings in Date Palm Rachis, as illustrated in Figure 14 (Mansour et al., 2017).

The considered properties to be measured are: Tension Stress, Longitudinal Modulus of Elasticity, Radial/Tangential Modulus of Elasticity, Longitudinal-Radial/Tangential Shear Modulus. These properties were considered according to the required properties for structural analysis for orthotropic materials in SAP2000; the most widely used software for structural analysis. The rest of the properties are to be measured in the upcoming papers.

The following properties were measured for ”Baladi” species of date palm trees in Minya governorate along the Nile Valley in the metalloids Laboratory and Polymers Laboratory in the Faculty of Engineering, Ain Shams University. The properties are carried out on the middle portion of the rachis using DIN EN 408-2004 standards with 12% moisture content.

Date palm rachis has been used for traditional construction using the pure instinct and experience of the rural builders in the rural areas in Egypt and the Middle East. However, the pre-construction structural analysis could help to make the date palm rachis-based structures more resistant to unpredictable forces like winds, seismic loads and onsite behaviors. This paper introduced the closest estimations of the mechanical properties of whole date palm rachis using the available equipment in the laboratories of the Faculty of Engineering, Ain Shams University.

Although date palm rachis is considered an anisotropic material, the linear orthotropic model was used to identify the axes of the material where the properties are to be measured. It was found that the properties of date palm rachis in the linear orthotropic model are supposed to be identical in the radial and tangential directions. The proposed date palm rachis properties are summarized in Table 2.

These properties cover most of the required properties to define Date Palm Rachis into structural analysis software like SAP2000. These findings prove that Date Palm Rachis is competitive to imported wood species in Egypt. This opens the door for further researches to structurally evaluate the potentials of Date Palm Rachis as a versatile building material that can be used as a substitute to expensive imported wood in Egypt.