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Penta-Ocean Construction Co., Ltd.

Tokyo, Japan - September 08, 2025 - The seven general construction companies (Asanuma Corporation, Okumura Corporation, Kumagai Gumi Co., Ltd., Penta-Ocean Construction Co., Ltd., Sato Kogyo Co., Ltd., Tekken Corporation and Yahagi Construction Co., Ltd.) collaboratively improved the "Construction method of reinforced concrete beam using various casting techniques with different concrete strengths (Dicos Beam Method)", and have obtained a renewed structural performance evaluation from Japan ERI Co., Ltd. on June 24, 2025 (Certificate No.: K19023-02^*1).

This method is related to the design and construction of a beam using concrete with different strengths in its upper and lower sections.

In the construction of reinforced concrete (RC) structures that utilize precast beams, it is a common practice to fabricate the lower section of the beam as a precast member (PCa), while the upper section of the beam is cast-in-situ concrete. In conventional construction methods, concrete for the upper section of the beam is typically of the same strength as its lower section, necessitating separate casting of the slab concrete.

By adopting this method, concrete of the same strength as the slab can be cast on the upper beam section, streamlining the construction process and thereby enhancing productivity. Moreover, this method can also be applied to structures that do not utilize PCa components.

This method utilizes concrete of varying strengths within a single beam cross-section. To assess the concrete strength of the beam, the concept of “equivalent average strength” is introduced, taking into account the cross-sectional areas and concrete strengths of the upper and lower sections of the beam, as well as the effect of the slab. Utilizing this concept, both allowable stress level and ultimate shear strength level can be effectively designed.

In the latest structural performance evaluation, the assessment method for equivalent average strength has been revised to streamline design practices, particularly when the slab elevation is lower than the elevation of the upper beam section, or when void slabs are employed, broadening the scope of application for this method.

Going forward, the participating general contractors plan to adopt the method primarily for their design and build projects involving RC structures, aiming to streamline the construction and improve productivity.

^*1This method was jointly developed by Asanuma Corporation, Okumura Corporation, Kumagai Gumi Co., Ltd., Penta-Ocean Construction Co., Ltd., , Tekken Corporation and Yahagi Construction Co., Ltd. and received a structural performance evaluation in November 2019 (Certificate No.: K19023). Sato Kogyo Co., Ltd. joined in July 2023 (Certificate No.: K19023-01)