$$\begin{aligned}l_d &= \frac{0.90\,d_b\,f_y}{\lambda\sqrt{f_{ck}}}\cdot\frac{\alpha\beta\gamma}{(c+K_{tr})/d_b} = \frac{0.90\times25.4\times400}{1.0\sqrt{30}}\times\frac{1\times1\times1}{2.50} \\ &= \boxed{\mathbf{668}\ \text{mm}}\ (26.3d_b) \\ \text{약산식 }l_{db} &= \frac{0.6\times25.4\times400}{\sqrt{30}} = 1113\ \to\ 1113\ /\ 1669\end{aligned}$$

$$\begin{aligned}c_b &= \min(c+d_{bv}+d_b/2,\ s/2) = \min(65.7,\ 67.2) = 65.7 \\ c_b/d_b &= \min(2.59,\,3.5) = 2.59 \\ l_d &= \frac{d_b\left(\dfrac{f_{fr}}{0.083\sqrt{f_{ck}}}-340\right)\psi_t}{13.6+c_b/d_b} = \frac{25.4\left(\dfrac{850}{0.083\sqrt{30}}-340\right)\times1}{13.6+2.59} \\ &= \boxed{\mathbf{2{,}400}\ \text{mm}}\ (94.5d_b)\end{aligned}$$

$$\begin{aligned}\alpha &= 1\ (일반),\quad \beta = 1,\quad \gamma = 1\ (D22 이상) \\ c &= \min(65.7,\ 67.2) = 65.7 \\ \frac{c+K_{tr}}{d_b} &= \min\!\left(\frac{65.7+0}{25.4},\,2.5\right) = 2.50\end{aligned}$$

$$\begin{aligned}\psi_t &= 1\ (일반) \\ c_b/d_b &= 2.59\ (\le3.5)\end{aligned}$$

$$\begin{aligned}l_d &= \max(668\times1,\ 300) = \boxed{\mathbf{668}\ \text{mm}}\ (26.3d_b)\end{aligned}$$

$$\begin{aligned}l_d &= \max(2400\times1,\ 20d_b = 508,\ 300) = \boxed{\mathbf{2{,}400}\ \text{mm}}\ (94.5d_b)\end{aligned}$$

$$\begin{aligned}l_{db} &= \max\!\left(\frac{0.25\times25.4\times400}{\sqrt{30}},\ 0.043\times25.4\times400\right) = 464 \\ l_d &= \max(464,\ 200) = \boxed{\mathbf{464}\ \text{mm}}\end{aligned}$$

$$\begin{aligned}l_{d,c} &= l_d = \boxed{\mathbf{2{,}400}\ \text{mm}}\end{aligned}$$

$$\begin{aligned}l_{hb} &= \frac{0.24\times1\times25.4\times400}{\sqrt{30}} = 445 \\ l_{dh} &= \max(445\times0.70,\ 8d_b = 203,\ 150) = \boxed{\mathbf{312}\ \text{mm}}\ (\text{꼬리 }12d_b = 305)\end{aligned}$$

$$\begin{aligned}f_{fu} &= 850\ \text{MPa}\ \to\ \text{구간 }520 < f_{fu} < 1040 \\ l_{bhf} &= 850\times25.4/(3.1\sqrt{30}) = 1272 \\ l_{dh} &= \max(1272\times0.7,\ 12d_b = 305,\ 230) = \boxed{\mathbf{890}\ \text{mm}}\ (\text{꼬리 }12d_b,\ r\ge3d_b = 76)\end{aligned}$$

$$\begin{aligned}l_{dt} &= \frac{0.24\times1\times25.4\times400}{\sqrt{30}} = 445\ \to\ \max(\cdot,\ 8d_b,\ 150) = \boxed{\mathbf{445}\ \text{mm}}\ (\text{그 외 부위 (4.1-7)})\end{aligned}$$

$$\begin{aligned}l_d^{(4.5.2)} &= 668\ (\text{300 최솟값 및 감소 미적용}) \\ l_{lap} &= \max(1.3\times668,\ 300) = \boxed{\mathbf{868}\ \text{mm}}\ (B급)\end{aligned}$$

$$\begin{aligned}l_d(f_{fu}) &= 2400\ (\text{최솟값 및 감소 미적용}) \\ l_{lap} &= \max(1.3\times2400,\ 20d_b = 508,\ 300) = \boxed{\mathbf{3{,}121}\ \text{mm}}\ (B급)\end{aligned}$$

$$\begin{aligned}l_{s1} &= \left(\frac{1.4\times400}{\sqrt{30}}-52\right)\times25.4 = 1276 \\ l_{s2} &= 0.072\times400\times25.4 = 732 \\ l_s &= \max\big(\min(l_{s1},l_{s2}),\ 300\big) = \boxed{\mathbf{732}\ \text{mm}}\end{aligned}$$

$$\begin{aligned}l_{lap,c} &= l_{lap} = \boxed{\mathbf{3{,}121}\ \text{mm}}\end{aligned}$$

$$\begin{aligned}\frac{\phi M_n}{V_u}+l_a &= \frac{300\times10^6}{180\times10^3}+150 = \boxed{\mathbf{1{,}817}\ \text{mm}} \\ l_d &= 668\ \le\ 1817\ \ \color{#0a8a2a}{\checkmark\ \textbf{OK}}\end{aligned}$$

$$\begin{aligned}\frac{\phi M_n}{V_u}+l_a &= \frac{300\times10^6}{180\times10^3}+150 = \boxed{\mathbf{1{,}817}\ \text{mm}} \\ l_d &= 2400\ >\ 1817\ \ \color{#d40000}{\times\ \textbf{NG}}\end{aligned}$$