size-dependent punching shear failure of thick reinforced concrete slabs

大厚度钢筋混凝土板的试验研究仍然是土木工程中的一大挑战。最重要的是，难以控制的试件尺寸、相关的自重和适当的测试载荷是目前面临真正极限的传统测试设置和概念的原因。这就解释了为什么国际上对RC板冲切性能的无阻尼密集研究仅限于相对较薄的构件，因此没有涵盖最近可能在未来进一步上升的全部实用范围。尽管存在这些实验缺陷，半经验设计规则(EC 2，ACI 318，MC 2010)是根据现有数据得出的，必须适用于超出预期范围的情况。因此，有必要对实验结果进行外推，这将增加由于尺寸效应而导致的冲切破坏预测的不确定性。如果不测试厚厚的RC板，就无法量化其是否存在潜在的安全问题，以及这些问题可能有多大。此外，基于这些数据提出的物理上可很好解释的模型还需要通过大规模试验进行进一步验证。在之前的项目阶段中不断发展和改进的总体概念旨在直接解决赤字，首次能够对真厚的RC板进行冲切试验。在数值模拟的启发下，由于试件的(多重)对称性，大大减少了对空间、试验装置、试验装置和载荷的试验要求。这使得可以利用手头已有的基础设施测试明显较厚的RC板。一旦在当前阶段成功地将无意的刚性摩擦环节减至最小，并在之前按照审查员的指示对30厘米厚的RC板进行了S功能验证，现在应最终测试70厘米厚的RC板。首先，这需要建造足够的、大规模的混凝土支架，这一点到目前为止一直被推迟。下一步是再次使用适当但对称缩减的梁来验证当时按比例放大的概念。最后，该提案包含两个测试系列。前者能够通过严格和真实的无筋钢筋混凝土板的试验来量化尺寸效应，而后者则通过试验捕捉到钢筋混凝土板的不同潜在破坏机理。

Experimental investigations of reinforced concrete (RC) slabs with significant thickness still represent a major challenge in civil engineering. Above all hardly manageable dimensions of test specimen, associated self-weights, and appropriate test-loads are responsible for conventional test-setups and concepts currently facing true limits. This explains why undamped intensive international research on the punching shear behavior of RC slabs has been limited to comparatively thin members and thus does not cover the total practical range of recent application that probably rises further in the future. Despite these experimental deficits semi-empirical design rules (EC 2, ACI 318, MC 2010) have been derived from the available data basis and must be applied to cases beyond the intended scope. Thus, extrapolation of experimental results is necessary which introduces additional uncertainty to prognoses of the punching shear failure due to the size effect. Whether potential safety issues arise thereof and how big these might be cannot be quantified without testing thick RC slabs. Also physically well-interpretable models based on these data which have been proposed yet need further verification by large scale tests. The general concept continuously developed and enhanced in the previous project phases aims to resolve the deficit directly, enabling for punching shear tests of really thick RC slabs for the first time. Inspired by numerical simulation, experimental demands concerning space, test-setup, devices and loads are significantly reduced accounting for (multiple) symmetry of specimens consequently. This allows for testing of clearly thicker RC slabs employing the infrastructure already at hand. Once having successfully minimized unintentionally stiff friction-links in the current phase and having restricted to demonstrate the test set-up´s validation of functionality to 30 cm thick RC slabs as directed by the reviewers before, now 70 cm thick RC slabs shall be finally tested. At first, this requires to build the adequate and large-scale concrete-made supports finally, which have been deferred so far. Next is to consequently verify the then up-scaled concept employing appropriate but symmetrically reduced beams again. Finally, the proposal contains two test series. The first enables to quantify the size effect by testing of strictly and truly up-scaled RC slabs without reinforcement while the second one captures the different potential failure mechanisms of reinforced concrete slabs experimentally.