Keywords

1 Introduction

1.1 Background

Umbrella-shape structure (US), innovated building form, usually uses in train station, markets and airports. Traditionally, the US is made up with the column and the umbrella surface.

The first US called “mike umbrella” was built in 1929 [1]. The “mike umbrella” was fabricated by the materials of concrete. Due to the limitation of the structural theory, the “mike umbrella” only used in pavilion [2]. With the development of the structural theory and materials, the US was adopted as the long-span structures like terminal and high-railway station [3]. Although the US widely used in the long-span structures, there were few US in the building. Some of them were used in the museum or memorial hall [4,5,6]. For the almost highway service area in China, the traditional building was adopted. The single building style caused aesthetic fatigue, as well as no conductive. However, the highway service area was the visiting card to the local city, the single building style of the highway service area may constrain the advertisement of the city.

1.2 Project Overview

Jixiang highway service area, locates in Longxun Highway, Heyuan City, is adopted the US as the design scheme. Specifically, the architectural design ideas of the Jixiang highway service area are mainly based on the flower called “Bougainvillea” in Heyuan City, Guangzhou Province, which is integrated with hexagonal umbrella-shape structures and is prefabricated using a “Lego-like” preassembly method (Prefabricated building). The overall design reflects the design ideas of environmentally friendly, green, environmental protection, and low-carbon, and the buildings of the service area are intermixed with clusters of the tufted rhododendron bush. While highlighting the theme of green and environmental protection, it also contains strong local cultural color, and has great visual effect (as shown in Fig. 1). Jixiang service area is being built into the most representative, interesting, innovative and avant-garde expressway service area building quality.

Fig. 1.
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US in Jixiang service area

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US in Jixiang service area is constructed by the method of prefabrication. Different parts of US are designed accordingly, and the parts of US are the concrete-steel combination structures. These parts are fabricated in the manufactory, which could ensure the quality of components. After casting, the components are conserve under controlled condition. Different parts are transported to construction site and assembled.

The construction method of the US is prefabrication, and the similar US was no existing. Thus, to verify the safety of the US, the test of the full-scale US is necessary. The load is applied to the top of the full-scale testing, and the structural response are recorded and analyzed to justify the safety of the US.

2 Experiments Program

2.1 Details of Umbrella-Shape Structure

The dimensions of the US were shown in Fig. 2. The horizontal length of the cantilever beam was 6000 mm, while the heigh of the column was 4740 mm. The steel tube column was combined with different thickness of steel tube. The thickness of top steel tube and of bottom was 14 mm and 5 mm, respectively.

Fig. 2.
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Details of the US

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2.2 Materials Properties

Table 1 listed the materials of US. The designed concrete degree was C35, while the rebars was HRB400. The designed strength of steel was Q355b.

Table 1. Materials of the US
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2.3 Testing Setup and Instrumentation

A testing setup as illustrated in Fig. 3. Considering the difficult of applying loads, a total of 13 bundle of rebars was adopted to load, each weight of bundle of rebars was 26 kN. The loading class of the test was listed in Table 2.

Fig. 3.
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Typical experimental setup of US

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Layout of measuring points of US was shown in Fig. 4. The vertical displacement of the end of cantilever beams was measured by the total-station. The strain gauge was arranged in the cantilever steel beam, concrete cantilever beams, and concrete column respectively.

Fig. 4.
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Layout of measuring points

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3 Results and Discussion

Table 2 summarized the maximum compressive/tensile stress of steel cantilever beam, maximum compressive stress of concrete columns, maximum compressive/tensile stress of concrete cantilever beams, and vertical displacement of the cantilever beam.

It can be seen that under the maximum loading load (338 kN), the maximum tensile stress of the cantilever steel beam was 32.96 MPa, and the maximum compressive stress was 19.98 MPa; The maximum compressive strain of the concrete column was 4.23 MPa; The measuring points of the concrete beam were all in a compressive state, with a maximum compressive strain of 4.98 MPa. All the strength of concrete and steel of US were small than their design strength respectively.

Table 2. Summary of the tested results
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3.1 Load-Displacement Curve of US

The load-displacement curve of US was shown in Fig. 5. It can be seen that the maximum displacement of the US was 4.9 mm when applied the load of 338 kN. According to the Fig. 5, the linear relationship between the load and displacement maintained under loading. It was indicated that the US was in elasticity stage when the load reached 338 kN.

Fig. 5.
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Load-displacement curve of US

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3.2 Strain of Cantilever Steel Beam

The load-strain curve of cantilever steel beam was illustrated in Fig. 6. It can be seen that the load-strain curve of the cantilever steel beam was in a linear stage. When the load reached 104 kN, the compressive strain in the lower part of the cantilever steel beam increased faster than the tensile strain in the upper part. However, when the load was greater than 104 kN, the growth rate of tensile strain was significantly faster than that of compressive strain. Finally, the maximum compressive strain of the cantilever steel beam was 100 με, while the maximum tensile strain was 159 με.

Fig. 6.
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Load-strain curve of cantilever steel beam

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3.3 Strain of Concrete Column

The load-strain curve of concrete column was illustrated in Fig. 7. It can be seen that before the load reached 208 kN, there was a linear relationship between the load and the strain of the concrete column. However, after 208 kN, the strain of the concrete column increased slowly, and the strain at the top of the concrete column at measurement point 4 even shown rebound.

Fig. 7.
figure 7

Load-strain curve of concrete column

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3.4 Strain of Concrete Cantilever Beam

The load-strain curve of concrete cantilever beam was illustrated in Fig. 8. It can be seen that under different load levels, the part near the concrete column at the root of the concrete beam was in a compressive state, and the maximum compressive strain occurs at the bottom of the beam, which was 184 με.

Fig. 8.
figure 8

Load-strain curve of concrete cantilever beam

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4 Conclusion

  1. 1.

    The US was in elasticity stage when loading, which Was reflected in load-displacement curve.

  2. 2.

    Under the final load (338 kN), the maximum compressive strain of the cantilever steel beam was 19.98 MPa, and the maximum tensile strain was 32.96 MPa, both of which were smaller than the yield strength of Q355b (355 MPa); The maximum compressive stress of concrete columns was 4.23 MPa, which was less than the strength of C35 concrete; The maximum compressive stress of the concrete at the root of the cantilever beam was 4.98 MPa, which was less than the strength of C35 concrete. The experimental results shown that under the final load, the internal forces of the steel plates, cantilever beams, and concrete columns of the structure were all less than their corresponding resistance, and the structure was in a safe state.