Added Values of the Local Timbers Materials for Main Bridge Frame Structures Utilizing Laminating Composites Technology

ABST CT: e objectives of this article are to seek the opportunity to enhance the local Indonesia timber material physical performances (encompassing the low-class quality of III and IV timbers with the Modulus of Elasticity (MOE) = 5,000 9,000 MPa) utilizing laminated composite technology to become higher-class timber quality (class II) with the Modulus of Elasticity (MOE)> 15,000 MPa so that it can be used as an alternative material for constructing the bridge mainframe structures (girder beams) especially for the Indragiri Hilir regency, Riau Province, Indonesia. is regency needs several hundred small-medium bridges for connecting 20 districts, 39 wards, and 197 villages using local materials such as local timbers. is laminating technology is not a new technology but the utilization of this technology for constructing the main bridges structures is challenging and limited to the implementation in the civil construction industrial sector. is study composed 2 types of the low-class quality (lcq) of timber materials (such as Shorea sp and Shorea peltata Sym) and 2 types of medium class-quality (mcq) ones (Dipterocarpus and Calophyllum) for constructing the main bridge structures. Based on the laboratory test results utilizing 80% of lcq materials and 20% mcq ones, these composite timber materials may increase the timbers MOE by 145% to 166% from the existing MOE value of the mcq solid timbers. Based on the simulations these laminated composites wooden bridge girders 2 x (70x20) m2, these timber materials have passed all the tests and the application of this technology may improve the lcq timber values and it could be used for an alternative material of the bridge girder's main structures.


INTRODUCTION
It was reported that the global growth in timber demand was increased from 334 million m 3 (2017) to 341 million m 3 (2018) (Canadian Forest Industry, 2019). e requirement of the timber materials type class I-II (Strength class I -II based on PKKI, 1961 and SNI 7973: 2013) [1,2] in Indonesia has been also continuing to increase [3,4]. In Indonesia during the 2016-2017 periods, the production of timber logs was estimated at 40 million m 3 per year. In fact, the existing plywood timber, sawn-timber, and pulp industries required 75.8 million m 3 annually. Hence, there was a lag of 35.8 m 3 legal timber logs per year [3]. e decrease in the area of the natural forests in Indonesia at the rate of more than 20 million hectares in 2016-2017 controversial with an increase of timber logs demand. e high demand and the lack of supply of quali ed and legal timber materials have implications for increasing the high-quality timber prices. For example the price of the timber quality class II -I per m 3 in Riau province currently reached Rp. 4,500,000 -Rp. 8,500,000, hence this caused to increase in wooden bridge costs and an increase in using illegal timber logs [3]. e timber class IV and III prices were about Rp. 2,500,000 per m 3 , which is far less (50%) than those the quality class II-I.
us, there was a need to seek alternatives timber technology to improve the low-class quality timber materials (class IV and III) to become high-class quality ones (class II-I) and at affordable prices by utilizing a combination of the existing local timber materials which is relatively low quality and relatively cheaper prices with relatively high-class quality timbers. ese combination timbers may be used as the alternative construction material of the girder bridge. Hence this can be performed by the application of laminated timber composite technology [5,6]. e laminated timber composite technology is not new because this technology combines materials that were made of two or more types of timbers that remain separate and different at the macroscopic level but mechanically can be considered as an integrated component [7][8][9].
It is interesting to investigate to what extent this composite technology in increasing the strength and physical properties of the low-class quality timbers to become medium or high-class quality timbers, which are ultimately these composite materials can be used as materials for constructing bridge girders [5]. e results of this investigation are expected may contribute to the body of knowledge in the area of composite materials for the civil engineering construction industry. ese article objectives are to explore the opportunity for enhancing the added values of the low-class quality of III and IV timber materials in Indonesian, especially in Indragiri Hilir to become a higher-class quality one (class II) utilizing laminated composite. e end of the result materials will be simulated to be used for constructing the bridge's mainframe structures. e case study area was located in Indragiri Hilir, Riau Province, Indonesia. Approximately 93.31% of the area of Indragiri Hilir Regency is situated on the river deposit areas, swamp, and wetland, with peat soil and brackish forest covering the coast of the Indragiri River.
is area encompasses 12,614 km² with an average altitude of 0-3 meters above the mean sea level. e Indragiri Hilir Regency has many rivers and thousands of km of ditches so that this area is known as " ousand Ditches Land (Negeri Seribu Parit)" so that it requires several hundred bridges especially small-medium bridges (length < 10 m) to connect 20 districts, 39 wards, and 197 villages. Commonly, the small-medium bridges were constructed using concrete materials that were experienced to collapse within 2-5 years periods as the effect of low bearing capacity soils so that the peat soils do not have any sufficient bearing capacity in supporting the concrete bridge foundations. e application of medium-high-quality timbers (class I-II) to construct wooden bridges in these areas was experiencing difficulty to purchase legally, and the costs were relatively expensive. Hence this is important to construct the bridge using low-and medium quality timbers that are available locally in the market and relatively inexpensive.

METHODOLOGY
e samples of timber material were obtained come from Indragiri Hulu District, Riau Province, Indonesia. e timber materials consist of timber classes of II, III, and IV, Epoxy Resin and Hardener, reinforcing sheets (mat) from polypropylene material [10][11][12][13].
is study composed 2 types of low-class quality (lcq) of timber materials (such as Shorea sp and Shorea peltata Sym) and 2 types of medium-class quality (mcq) ones    State of the arts in the application of the low-medium timbers has historically been used as non-main construction materials such as partitions and the oor surface. is study will explore the added value in using these materials as a main structural material for bridge mainframes. It was also acknowledged that Dipterocarpus is known as Keruing and Calophyllum is known as Kuras. Both timbers are classi ed as fast-growing trees and very rare to be applied in constructing bridge frame structures. Hence, this research study may challenge the academic approaches in developing a low-class timber material to become high-class timber materials that can be used as a structural material. In this study, there were used 2 types of a composite of timber planks with a ratio of 20% of high-class quality timbers (2 types of timbers medium-high-class II) and these were combined with 80% the low-class timbers (2 types of low-class III and IV quality). ese timber composite materials were then a ached with epoxy resin and hardener, so it becomes a composite laminated timber or glued laminated timber (glulam). (Figure 3). e importance of improving the low-class quality of timber materials into high-class quality one, especially for constructing bridge beams should pass the test standards of the shear and exural forces test and loads test before they can be recommended to apply in the construction industry area [14]. e shear forces that occur in the beam structure can be either vertical or horizontal shear forces, the maximum horizontal shear stress will occur on the neutral axis of the cross-section of the beam [15]. e behavior of shear stresses in the beam is illustrated in the following gure ( gure 4). e composite beams can be formed with two different qualities of timbers. e high-class quality timbers' strength was placed on the outside (the top and the bo om layers), and the lower-class timber was placed at the inner layers of this composite with lower-class quality timbers [6,7] as shown in gure 5. A er the timber samples were glued with epoxy materials then were pressed evenly for 24 hours (Figure 6 a,  b, c). e samples were also tested for the identi cation of their mechanical properties using a Universal Testing Machines (UTM) (Figure 6 d, e, f). e samples were placed in two points with a distance of one-third of the timber spans. e dedicated samples were loaded gradually at a constant loading speed of up to 18 MPa in 30 seconds. en reduce the loading slowly to 5 MPa, then increase the load to 18 MPa, and then decrease it again to 5 MPa. During the cycle of up-and-down loading tests, the de ections that occur in less than 10 seconds during the loading of 7 MPa and 18 MPa were recorded (Figure 6f).
According to Harry Ga erer (2017), there was a success story in establishing an 84 meters high building using timber structures in Vienna, Austria [5]. Hence, there was a proves that the timber could be the main structure for civil construction materials as long as they pass the loading test standards.
Muthmainnah (2014) has conducted a test that results in the compressive strength value of laminated wood depending on the position of the load on the timber surface [16]. e compressive strength with the position of the load plate in the middle of the laminated timber surface produces a higher compressive strength value compared to laying the load on the edge of the laminated timber surface.
However, it was also identi ed that the laminated timbers may have some weaknesses including this material are relatively easy to cause res. Harry Ga erer (2017) and Muthmainnah (2014) study tested various cross-laminated timbers for the structural columns and wooden panels. e results showed that the materials were relatively poor in resisting any re occurrences as the behavior of the adhesive used to bind cross-laminated is prone to cause res [17,18]

RESULTS AND DISCUSSION
is study conducted various tests for composite laminated timbers (glulam) using bending and shear tests.
en the results were simulated using vehicle standard axle load encompassing dead load and life load.

Bending Strength Test Results
Based on the test results for the beam exural test (referring to the ASTM D 143-94 standard) [19], it was identi ed that high-class quality timbers such as Dipterocarpus and Calophyllum (Keruing and Kuras timbers) were classi ed as E13 timber quality code values.
Meanwhile for low-class quality timbers such as Shorea sp and Shorea peltata Sym ( e timber quality codes of E6, E8, E9, and E10 were based on PPKI-1961 codes [1]. us it can be summarized that the timber laminate composite technology utilizing low and high-class quality of timbers as a beam composite was able to increase the exural strength and modulus of elasticity of timber material from an average of 5,080 MPa (Shorea peltata Sym) to 8,415 MPa (Composite), and from an average of 7,705 MPa to 11,194 MPa as shown in Table 1 Figure 8). Shorea sp and Shorea peltata Sym are more likely to be more bri le, and lower in bearing stress-strain load. A er compressing compression load tests were conducted these both timbers were damage within similar areas at the upper side of timber layers (Figures 9 and 10).  showed that the model of damage started to occur at the bo om layer of the Shorea peltata Sym timber, then it was followed by the release of a layer of the glued timber that spreads along with the timber layers ( Figure 6). e results of exural testing of Dipterocarpus timber composites of 20% or 1/5 part with Shorea sp timber (80%) obtained the type of exural damage type where the initial damage occurred on the bo om Keruing timber ber as shown in Figure Based on the results of the MOR test and load-de ection relationship graph shows a relatively large increase in deformation and ductile behaviors, this is due to the contribution of high-quality timber layers (Dipterocarpus and Calophyllum) which are more resilient compared to low-quality timber species. e damage areas were drawn in Figure 9.

Shear Strength Test Results
Tests of timber laminated sliding blocks that were compiled using two types of adhesives (Epoxy-bond Brand adhesive based on Epoxy and Cross-bond X4 based on PVAC ones) have yielded the following results (Table 3).
Based on Table 3, as well as Figure 10 it can be stated that the results of the shear strength test results for the Dipterocarpus and Shorea peltata Sym timber types are eligible for Epoxybond and Cross-bond X4 adhesive types, while for the Calophyllum and Shorea sp timber types do not meet the requirements. For gluing using Crossbond X4 adhesives are eligible for all types of the tested timbers ( Figure 10).  Live loads Point loads with the assumptions of p loads = 4.36 ton (Based on the 66% of the equivalent single axle load (for rear wheel excel truckload) of 1.2 L with the total truck weight of 6.6 ton was 66%x6.6 ton = 4.36 ton) (Fig. 12).
e average truck total loads in Indragiri Hilir, 2019 will pass the dedicated bridge was 6.6 ton

CONCLUSION
Based on the laboratory and the simulation tests, it was concluded that timber beams which were performed by two different types of timber materials (using a laminated composite technology) could be used for bridge beam materials especially for the wooden bridge structure. e use of a high quality-class II timber material (20% Dipterocarpus timber) and composited with the low quality-class III (80% Shorea peltata Sym timber material) could produce higher MOE timbers, which is compatible with 145% to 166% of the existing lower-class pure quality of the timber material one. Hence, it is recommended that to perform validations and tests in the relevant environment prior to the implementation of this material to the civil construction engineering area.